After 58 games over two seasons with the Lightning, Kelly was sent to the New Jersey Devils prior to the 1999–2000 season, where he spent the majority of the season with their AHL affiliate, the Albany River Rats. Kelly notched 57 points for Albany, but made just one appearance with the Devils. However, injuries during the Devils' playoff run forced Kelly into the NHL lineup, where he appeared in 10 games during the Devils' Stanley Cup winning drive. In February 2001, after 25 games in New Jersey, Kelly was traded to the Los Angeles Kings for forward Bob Corkum. With L.A.'s AHL affiliate, the Manchester Monarchs, Kelly enjoyed his best statistical seasons as a pro, amassing 133 points in just 113 games from 2002–2004, and representing the Canadian All-Stars in the 2004 AHL All-Star Classic.

Following the 2003–2004 season, Kelly signed in Germany's Deutsche Eishockey Liga with the Mannheim Eagles. In November 2005, Kelly signed with the Frankfurt Lions of the same league, where he scored 20 points in 22 games. In 2007, he signed with the Minnesota Wild and spent much of the season with the team's AHL affiliate, the Houston Aeros before being called up at the end of the season to fill in at center. After being signed by Columbus Blue Jackets and sent down to their affiliates Syracuse Crunch, Kelly chose to return to Europe by signing a one-year-contract with HDD Tilia Olimpija Ljubljana in Erste Bank Eishockey Liga.[1] However, after posting 3 points in only his second game in the 2009-10 season, Kelly suffered a season ending injury and decided terminate his contract and retire from professional hockey to return to Canada.[2]

While showing promise at the beginning of his pro career, most would regard him as the 'biggest bust' of the 1995 NHL draft. Many Oilers fans use Kelly as an example of the Oilers' inability to draft NHL level players. Most fans and media expected the Oilers to draft Shane Doan—an obvious choice who was drafted next by Winnipeg and later become the face and captain of the Jets/Coyotes franchise—but shocked everybody by drafting Kelly 6th overall.